Monolithic integrated circuit technology has been increasingly directed to the production of high speed, high performance bipolar semiconductor devices, such as bipolar RAMs, etc. The performance of integrated circuits incorporating these bipolar devices is sensitive to the spacing between the emitter and the base contact of the device, advance electron beam photolithography being capable of reducing this distance to 2-3 microns. Even greater reduction in spacing is known, as described in U.S. Pat. No. 4,160,991.
A large number of increasingly important applications for semiconductor devices of this type require the devices to be "radiation hard", i.e., capable of performing in high radiation environments which would hamper or disrupt the operation of a device otherwise unshielded. The inventor has developed a process for the production of high speed bipolar devices, in particular, RAMs, which are radiation hardened. The process relies, in part, on complete self-alignment of collectors, bases and emitters, through the use of patterned deposited silicon nitride.
Accordingly, it is an object of this invention to provide a process whereby radiation hard bipolar semiconductor devices may be fabricated.
It is another object of this invention to provide a process for the fabrication of high speed high performance radiation hardened bipolar RAMs. The achievement of these and other objects will be apparent to those of skill in the art through the detailed description provided below.